Index: lib/Target/X86/X86FixupBWInsts.cpp
===================================================================
--- lib/Target/X86/X86FixupBWInsts.cpp
+++ lib/Target/X86/X86FixupBWInsts.cpp
@@ -265,6 +265,11 @@
     return false;
 
   if (SubRegIdx == X86::sub_8bit) {
+    // We've checked that the 32-bit super register isn't live, but the
+    // 16-bit form might still be live.
+    unsigned DestReg16 = getX86SubSuperRegister(OrigDestReg, 16);
+    if (isLive(*OrigMI, LiveRegs, TRI, DestReg16))
+      return false;
     // In the case of byte registers, we also have to check that the upper
     // byte register is also dead. That is considered to be independent of
     // whether the super-register is dead.